C(sp3)-H Fluorination with a Copper(II)/(III) Redox Couple

Despite the growing interest in the synthesis of fluorinated organic compounds, few methods are able to incorporate fluoride ion directly into alkyl C-H bonds. Here, we report the C(sp 3 )-H fluorination reactivity of a formally copper(III) fluoride complex. The C-H fluorination intermediate, L CuF, along with its chloride and bromide analogs, L CuCl and L CuBr, were prepared directly from halide sources with a chemical oxidant and fully characterized. While all three copper(III) halide complexes capture carbon radicals efficiently to afford C(sp 3 )-halogen bonds, L CuF is two orders of magnitude more efficient at hydrogen atom abstraction (HAA) than L CuCl and L CuBr. Alongside reported kinetic data for other L Cu(III) species, we established a positive correlation between ligand basicity and the rate of HAA. The capability of L CuF to perform both hydrogen atom abstraction and radical capture was leveraged to enable fluorination of allylic and benzylic C-H bonds and α-C-H bonds of ethers at room temperature.